A roof reinforcement serves as a roof framework and is mounted on right and left side roof rails along the lateral direction of an automotive vehicle. The roof reinforcement, which has a wide portion at its center, is located between front and rear roof rails (see Japanese Laid-Open Patent Publication No. 2001-301653; hereinafter, “Reference 1”).
The roof reinforcement has a reversed hat-shaped cross-section for ensuring the strength and rigidity of a roof panel. A bottom surface of the roof panel is bonded to a flange portion of the roof reinforcement through the use of an adhesive.
In a conventional roof structure in which the roof panel is bonded on the roof reinforcement by an adhesive, a resonance frequency that can significantly deform the framework of the vehicular body is close to a resonance frequency of the roof panel. Further, an amplitude of the roof panel may increase by a resonance between the framework of the vehicular body and the roof panel. When the amplitude of the roof panel vibration increases due to resonance, the noise generated from the roof panel becomes louder and a muffled sound may generate.
The generation of the muffled sound depends on both the resonance of the roof panel and the cavity resonance of a compartment in a vehicle. That is, the muffled sound is generated when the resonance frequency of the roof panel is equal to or greater than a frequency of the cavity resonance. The cavity resonance mainly depends on the size and shape of the compartment. In order to prevent the muffled sound, it is required to reduce the resonance frequency of the roof panel to less than the frequency of the cavity resonance. In other words, the vibration of the roof panel should be restrained.
However, in the roof structure (a vehicular body structure) disclosed in Reference 1, only one roof reinforcement having the wide portion at its center is located on the intermediate portion between the front and rear roof rails and mounted on the right and left side roof rails of a vehicular body. Accordingly, when a range in which the roof reinforcement supports the roof panel is small and the resonance occurs at the vehicular frame (i.e., a body structure) due to the vibration of an engine, etc., it is not possible to effectively restrain the vibration of the roof panel.